Method of sublimation



1 March 13, 1928. 1,662,056

C. FIELD METHOD OF SUBLIMATION Filed March 22, 1920 10 A5 WK 4 3 w w 36 i6 g M E Z7 m wum'vfoz Patented Mar. 13, 1928.

UNITED STATES CROSBY FIELD, OF MAHWAH, NEW JERSEY, ASSIGNOR T NATIONAL ANILINE &

PATENT OFFICE.

CHEMICAL 00., INC., OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD OF SUBLIMATION.

Application filed March 22, 1920. Serial No. 867,821.

This invention relates to an improved method of sublimation, intended for the sublimation of anthracene, anthraquinone, etc. More particularly theinvention relates to an improved method for carrying out the sublimation operation in a substantlally continuous manner, and with avoidance of objectionable dusting or mechanical carrying over of undistilled particles, as well as with other advantages hereinafter set forth.

The invention will be further described in connection with the accompanying drawingillustrating an improved apparatusin which the improved process can be practiced; but it will be understood thatthe invention is illustrated by, but is not limited to, the specitic embodiments thereof so illustrated and described.

In the accompanying drawing Fig. 1 shows, in a somewhat conventional and diagrammatic manner, an improved sublimation apparatus in central vertical section, and with parts in elevation; and

Fig. 2 is a sectional view of part of the apparatus showing a modified construction.

The vessel or receptacle 1 consists of comparatively heavy material, such as cast iron, surrounded by a heating jacket 2, and having the vapor outlet pipe 3 leading tothe condenser 4. The superheated steam, -hot air, or other heated vapor or gas, is introduced through the pipe 5 and the branches 6 and 7 tot e jacket 2 and to the inside of the receptacle 1, the pipe 7 terminatlng in a series of perforated coils 8. The receptacle 1 is alsoprovided with a feeding hopper 9 having valves 10 and 11 therein, while the outlet vapor pipe 3 has a valve 12 therein. The receptacle 1 is also provided with an agitator 13 suitably rotated by a shaft passing through the stufiing box 14 and driven by a suitable gear 15. A perforated pipe 17 is also provided in the top of the receptacle for the introduction of a spray of water or cooling medium supplied through the pipe 16 having therein a regulating valve 18. The receptacle is also provided with a bottom discharge opening having a suitable valve or closure 19. The receptacle 1 may he condenser 4 is steam is introduced through the pi s 6 and i 7 to the jacket and to the inside 0 the vessel 1 so that the walls of the vessel are thoroughly heated. The steam is then shut ,ofi I from the inside of the apparatus by closing the valve 28 (the valve 22 also being closed), and a small proportion of the material to be sublimed, such as anthraquinone, is fed through the hopper 9 into the receptacle l. As there is no steam passing int'othe vessel at the time the material is-thus introduced-, dusting is eliminated exceptin that caused by the falling of the materia, and this is held in the vessel 1 by means of the damper 12 which is closed. The material coming in contact with the preheated walls of the vessel WlllCll have bee-n heated to a temperature above the melting point of the material, immediately absorbs heat therefrom and in so doing becomes plastic, this action being assisted by the agitator 13. When the material has become plastic, the damper 12 isopened, and the valve 28 is opened to permit the introduction of hot gas to the pipe 7 and coil 8, so that the material is subjected to the action of the steam thus introduced and sublimation begins, the sublimation be mg promoted by the heated walls of the receptacle as well as by thesteam or hot gas introduced through the coil 8, and this sublimation being promoted by the agitation.

When the temperature hasagain reached its first high point within the apparatus, the damper 12 and the valve 28 are again closed, the valves 10 and 11 opened, and another charge is introduced; and this loading cycle is continued'until a full charge has been introduced into the receptacle. By proceeding in the manner above described, with gradual and intermittent addition of further amounts of anthraquinone, and heating of the charges so introduced, the sublimation can be effected in such a manner as to obtain a practically continuous operation of the process, except for such interruptions as are required by the addition of further increments of the charge. Furthermore, by continuing the addition of further amounts of anthraquinone, as that contained in the receptacle is gradually carried over by sublimation, the operation can be continued for relatively long periods of time, with greatly increased capacity f the apparatus, as well as more accurate ntrol of conditions therein which affect the equality and yield of the sublimate.

As the process is continued, the fresh amounts of anthraquinone added are brought into contact with a large amount of heated material, but this will not interfere materially with the continuity of the operatlon (except for the time required for charging) since the material. previously charged has attained the requisite tem erature for sublimation, and the sublimation of such material will continue when the steam is again turned on and while the fresh 1ncrements of the charge are being brought to the requisite temperature.

When the sublimation has continued to a point such that the amount of non-sublimable material remaining in the receptacle 1 is large, the steam supply is shut off, and a spray of Water or other cooling medium is introduced through the perforated pipe 17. This causes the residue to solidify m the form of granules and break off from the sides of the receptacle and from the pipes and other metal parts. When this has been accomplished, the water spray is shut off and the discharge valve 19 at the bottom of the rece tacle opened so that the residue Wlll be disc arged. The residue can thus be removed'without completely cooling the vessel 1, and in a relatively short time and with consequent economy, and the vessel can be again charged and the cycle again started. By removing the residue without completely cooling the receptacle, heat losses are reduced. A similar reduction in heat losses is efiected by the jacket 2 and by the insulating coating or lagging (not shown) above referred to.

The arrangement of the pipes 6 and 7, together with the valves 21, 22, 23, 24 and 28, permits the operation of the apparatus 1n one or the other of the following ways:

(1) With the valves 23, 22 and 28 closed and the valves 24 and 21 open, the steam, which may be at a high pressure and temperature, will flow through the jacket 2 and thence to the atmosphere or to other apparatus where it is to be used.

(2) With the valve 28 closed and with the valves 23, 24, 22 and 21 open, the steam will flow through the jacket to the atmosphere or to other steam-consuming apparatus and will also flow through the body of material in the vessel 1. The relative amounts of steam can be controlled by opening or partially closing the valve 21.

(3) With the valves 21, 22 and 23 closed and the valves 28 and 24 open, the steam will fiow through the jacket 2 and thence through the pipe 7 and the coil 8 into the material in the receptacle 1.

The material which is sublimed and which is carried over with the steam into the condenser 4 is condensed therein, together with the steam by means of the water spray, and the condensed material is separated from the water by filtration or otherwise.

The following more detailed description will further illustrate the invention as applied to the sublimation of anthraquinone and anthracene respectively.

In the treatment of anthraquinone, the crude antbraquinone is charged into the receptacle 1 in the manner above described, and superheated steam is supplied from the superheaters at a temperature of about 410 C. The temperature of the steam as it leaves the jacket is about 315 C. while the average temperature of the interior of the sublimer is about 300 C. The temperature within the receptacle may advantageously be raised to about 350 C. before charging in order to offset the cooling effect when a new charge is introduced. The temperature of the condensate as it leaves the condenser may vary somewhat, but is ordinarily about 50 (1., about 25 above that of the cooling water employed. The steam may thus be introduced into the sublimer at a pressure of about 5 lbs. per square inch, depending upon the body of material through which it is caused to pass. The steam which passes through the jacket and does not enter the interior of the sublimer is diverted into a low pressure steam line through the valve 21.

In the sublimation 0t authracene, the temperature can be reduced about 50 below that for anthraquinone, although higher temperatures may be used comparable with those used where anthraquinoneis being sublimed.

In the modified structure illustrated in Fig. 2 the bottom of the receptacle 51 has a double wall with an opening 52 therein placed near the interior of the vessel. This opening or cavity 52 may be filled with a suitable material having a high specific gravity and high specific heat, through the pipe 53. The jacket 54 is similar in construction to that of Fig. 1.

From the foregoing description it will be seen that the improved process of the present invention provide for the carrying out of the subliming operation in a practically continuous manner and with greatly increased capacity and with reduction of loss of heat during the operation. The process is well adapted for large scale operations, and particularly for the sublimation of anthraccne and anthraquinone. In the operation of the apparatus and the practice of the process of the invention, the material to be Sllblllllt'll will, as above explained, he charged into the apparatus in a series of successive charges until a full charge has been introduced, and thereafter in successive charges to make u for the material that has been sublimed until the residue has increased to such an extent as to make it desirable to complete the subli- -mation of the charge then contained in the apparatus and then remove the residue in the manner above described.

I claim:

1. The method of effecting the sublimation of anthracene, anthraquinone, and the like which comprises charging the material in a finely divided state into a preheated subliming receptacle and stirring the material therein until it becomes plastic, and then passing a heated gas or vapor through the receptacle to promote the sublimation.

2. The method of effecting the sublimation of anthracene, anthraquinone, and the like which comprises charging the material in successive charges into a preheated sublimating receptacle, heating and agitating the material after each added charge until the charge becomes plastic, introducing into the charge after it has become plastic a heated gas or vapor, and continuing the addition of further amounts of material as that contained in the receptacle is sublimed, whereby the sublimation operation is carried out for considerable periods of time in a substantially continuous manner.

3' The method of efiecting the sublimation of anthracene, anthraquinone, and the like, which comprises introducing the material in a finely divided state into a preheated sublimation receptacle in a series of successive charges, heating the material after the introduction of each charge until it becomes plastic and introducingsuperheated steam after each such preheating operation to promote the sublimation, continuing the addition of further amounts of material and the further sublimation until a considerable amount of the residue has accumulated, and then removing the residue.

The method of efiecting sublimation of anthracene, anthraquinone, and the like, which comprises charging the material into a subliming receptacle, heating the material therein by heat interchange through the walls of the receptacle so that the material in contact with the heated walls becomes plastic, scraping the plastic material from said walls to permit further amounts of material to come into contact therewith, and thereby bringing the charge to a plastic condition, and introducing heated gas or vapor within the body of the material to promote the sublimation.

5. The method of effecting the sublimation of anthracene, anthraquinone, and the like, which comprises charging the material into a sublimating receptacle, stirring the charge and heating the same until plastic, continuing the stirring and introducing a heated gas or vapor to promote the sublimation, and removing the residue, at the end of the sublimation, by stirring and spraying the hot residue with a cooling liquid to efl'ectpulverization thereof, whereby the residue'can be rapidly removed and the receptacle made preheating a subliming vessel having walls of appreciable thickness to a point of temperature somewhat above the melting point of the material, introducing a small charge into this heated vessel, which charge is rapidly melted by abstracting heat from the walls of the vessel, and subsequently passing a heated gas through the vessel to carry away the sublimate.

7. The method of. continuously subliming anthracene, anthraquinone, and the like, which comprises preheating a vessel having walls of appreciable thickness to a point of temperature somewhat above the melting point of the material, introducing a small charge into this heated vessel and agitating the charge, whereby the charge is rapidly melted with lowering of the temperature of the walls of the vessel slightly, heating the vessel and passing heated gas therethrough to sublime the material, and adding successive charges with agitation and alternate passing of the heated gas through the chamber after the heated increments of the charge have become melted.

8. The method of removing the residue from the sublimation ot' anthracene, anthraquinone, and the like, from the sublimation receptacle at the end of the sublimation which comprises spraying the residue while sill at a high temperature from the sublimation with water while agitating the same in the hot receptacle and thereby efiecting pulverization or the residue, and removing the pulverized residue.

9. The method of subliming anthracene, anthraquinone and the like,wh1ch comprises preheating a vessel having walls of appreciable thickness to a temperature somewhat above the melting point of the material, feeding the material into the preheated chamber with agitation and, after the material has become melted, circulating superheated steam through the chamber an through the material therein to effect the sublimation and carry away the sublimate.

11. The method of effecting the sublimation of anthracene, anthraquinone, and the like, which comprises charging the material into a subliming receptacle, stirring the charge and heating the same, and introducin a heated gas or vapor to promote the sublimation, and subjecting the residue at the end of the sublimation to a spray of cooling liquid while subjecting it to stirring and thereby efi'ecting pulverization of the residue without cooling the receptacle to the temperature of the cooling liquid, whereby the residue can be rapidly removed and the receptacle made ready for a subsequent operation.

12. The method of effecting the sublimation of anthracene, anthraquinone, and the like, which comprises subjectin the material to sublimation in a heate receptacle with agitation and with the introduction of a heated gas or vapor, introducing further amounts of material to be sublimed and continuing the sublimation until the amount of nonsublimable material remaining in the receptacle is large, discontinuin the supply of heated gas or vapor, and w iile continuing the stirring, introducing a water spray to cause the residue to granulate, and discharging the residue from the receptacle in granular form without completely cooling the receptacle, whereby the residue can be removed in a relatively short time and the vessel made available in a still heated condition for further sublimation.

13. The method of subliming anthracene, anthraquinone, and the like, which comprises introducing successive small portions of the charge of the material to be sublimed into a subliming apparatus already containing material heated above the melting point of the material charged, with agitation of the material and continuation of the heating of the charge, and subsequently passing heated gas throu h the vessel to assist in carrying away the su limate.

14. The method of subliming anthracene, anthraquinone, and the like, which com rises carrying on the sublimation under conditions to give a large amount of heated material in the subliming apparatus, heated to a temperature above t e melting point of the material to be sublimed, and adding successive smallamounts of the material to be sublimed, with agitation of the heated material, and with continuation of the heating, whereby the added amounts of material are rapidly heated, and passing a heated gas through the vessel to carry away the sublimate from the heated char e.

In testimony whereof I a x my signature.

CROSBY FIELD. 

